A method for controllable high-precision light-curing 3D printing of combustible shells

Abstract

A method for controllable, high-precision photocuring 3D printing of combustible cartridge cases relates to a method for molding combustible cartridge cases. This method aims to address the technical issues of low molding precision and high surface roughness associated with existing 3D-printed combustible cartridge cases. The method comprises uniformly mixing a photocurable resin, a photoinitiator, a reactive diluent monomer, an energetic filler, and a photoinhibitor to obtain a slurry; then, adding the slurry to the trough of a photocuring 3D printer and performing 3D printing to obtain a controllable, high-precision combustible cartridge case. The 3D-printed combustible cartridge case of the present invention has a dimensional accuracy of 25 to 50 microns, an average tensile strength of 6 to 7 MPa, an average flexural strength of 10 to 11 MPa, and an average compressive strength of 36 to 40 MPa. The method can be used in the field of ammunition production.

Description

Technical Field

[0001] The invention relates to a molding method of a combustible powder shell. Background Art

[0002] With the increasing demand for combat performance of weapon systems by modern troops, the research and development of lightweight ammunition has received attention, and lightweight cartridge cases have emerged. Combustible cartridge cases made of combustible materials completely burn out the combustible material part after ignition, eliminating the need for shell extraction, shell ejection and corresponding mechanisms, increasing the firing rate while also providing a certain amount of launch energy. Since the emergence of combustible cartridge cases, their processing technology has always been a research focus. The existing combustible cartridge case is a loose, porous, and non-homogeneous material. It is mainly made of nitrocellulose, paper fiber, adhesive and diphenylamine mixed in a certain proportion and prepared by filtration molding. However, this method requires the design and processing of a molding mold first. Not only does it have low molding precision and a long cycle, but it also has poor uniformity and poor mechanical properties.

[0003] 3D printing technology has the advantages of speed, high resolution, and excellent spatiotemporal control, and has been proven to be a powerful tool for manufacturing models with desired designs and complex structures. However, the current 3D printing technology for combustible shells still has the disadvantages of low molding accuracy and high surface roughness. Summary of the Invention

[0004] The present invention aims to solve the technical problems of low molding precision and high surface roughness of existing 3D printed combustible shells, and provide a method for controllable high-precision light-curing 3D printing of combustible shells.

[0005] The method of the present invention for controllable high-precision light-curing 3D printing of a combustible charge shell is carried out according to the following steps:

[0006] 1. Mix 100 parts of photocurable resin, 5 parts of photoinitiator, 25-80 parts of reactive diluent monomer, 50-90 parts of energetic filler and 0.1-0.2 parts of photoinhibitor in parts by weight to obtain a slurry;

[0007] The light-curable resin is one or a combination of polyurethane acrylate, epoxy acrylate, polyester acrylate, and unsaturated polyester;

[0008] The energetic filler is one or a combination of 2,4,6-trinitrotoluene (TNT), hexanitrohexaazaisopentazolidine (CL-20), 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX), and 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX);

[0009] The photoinhibitor is one or a combination of carbon black, titanium dioxide, silicon dioxide, zinc oxide, zinc barium, methyl orange, Sudan III, methylene blue, and rhodamine B;

[0010] 2. Add the slurry into the material tank of the light-curing 3D printer and perform 3D printing with a layer thickness of 0.025mm to 1.0mm. Use a UV light source with a wavelength of 254 to 435nm and a power of 100 to 120mV for light curing. The exposure time of a single layer is 2 to 3s. After 3D printing, a controllable, high-precision combustible shell is obtained.

[0011] Furthermore, the particle size of the energetic filler described in step 1 is in the range of 30 to 500 μm.

[0012] Furthermore, the photoinitiator in step 1 is one or a combination of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO), ethyl 2,4,6-trimethylbenzoylphosphonate, phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide (819), and 1-hydroxycyclohexylphenyl ketone (184).

[0013] Furthermore, the active diluent monomer in step 1 is one or a combination of monofunctional isobornyl methacrylate (IBOMA), ethoxyethoxyethyl acrylate (EOEOEA), and tripropylene glycol diacrylate (TPGDA).

[0014] The slurry formulation plays a crucial role in the molding of the combustible shell of the present invention. The combustible shell formulation mainly consists of four parts: a photoinitiator, a photocurable resin, a reactive diluent monomer, and an energetic filler. The photocurable resin is a large part of the photocurable system and is a fundamental component of the combustible shell formulation, determining the basic properties of the cured product, including hardness, flexibility, adhesion, and other properties. In a photocurable resin system containing an energetic filler, the introduction of the energetic filler not only increases the viscosity of the system and easily causes sedimentation, but also the energetic filler crystal particles themselves have an excessively strong scattering ability for ultraviolet light, which can lead to the extension of the cured edge. By adding reactive diluents and photoinhibitors, high-precision printing controllability is achieved and the mechanical properties of the material are improved. The dimensional accuracy of the 3D-printed combustible shell of the present invention is between 25 and 50 microns, with an average tensile strength of 6 to 7 MPa, an average flexural strength of 10 to 11 MPa, and an average compressive strength of 36 to 40 MPa.

[0015] The present invention's controllable, high-precision, light-curing 3D printing method for combustible cartridge cases allows for the production of combustible cartridge cases through 3D printing. This method features a simple, rapid process, high structural flexibility, and produces uniform, high-performance combustible cartridge cases. The method is potentially applicable to ammunition production. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a photo of the controllable high-precision combustible cartridge cover prepared in Example 1;

[0017] Figure 2 This is a scanning electron microscope photograph of the fracture cross-section of the upper cover of the controllable high-precision combustible charge prepared in Example 1;

[0018] Figure 3 This is a tensile performance test curve of the controllable high-precision combustible cartridge prepared in Example 1;

[0019] Figure 4 This is a curve chart of the bending performance test of the controllable high-precision combustible cartridge prepared in Example 1;

[0020] Figure 5 This is a compression performance test curve of the controllable high-precision combustible cartridge prepared in Example 1;

[0021] Figure 6 This is a photo of the combustible cartridge cover prepared in Comparative Example 1;

[0022] Figure 7 This is a photo of the combustible powder shell prepared in Example 2. DETAILED DESCRIPTION

[0023] The following are specific embodiments of the present invention, and the technical solutions of the present invention are further described in conjunction with the embodiments, but the present invention is not limited to these embodiments.

[0024] Example 1: The method of controllable high-precision light-curing 3D printing of a combustible charge shell of this embodiment is carried out according to the following steps:

[0025] 1. Weigh 100 g of epoxy acrylate, 3 g of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO), 50 g of isobornyl methacrylate (IBOMA), 70 g of 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX) crystal particles with an average particle size of 30 μm, and 0.1 g of methyl orange and add them to a container in sequence. Stir in the dark at a speed of 456 r / s for 2 h to obtain a slurry;

[0026] 2. Pour the slurry into the material tank of the light-curing 3D printer and perform 3D printing under the conditions of a light source wavelength of 405nm, a power of 120mV, a printed layer thickness of 0.05mm, and a single layer exposure time of 2s to obtain a controllable, high-precision combustible shell.

[0027] The photo of the controllable high-precision combustible shell obtained in this embodiment is shown in FIG. Figure 1 As shown, it is the upper cover of the combustible powder shell.

[0028] The size of the upper cover prepared in this embodiment is consistent with the size of the design drawing. The diameter error of the upper cover is 20 microns, which is extremely small. The surface is smooth and delicate without obvious layer patterns. It can accurately restore the tiny details in the design. The layer thickness is uniform and thin, and the material utilization rate is high, so that there is little need for post-processing, or even no post-processing is required, saving time and cost.

[0029] The cross section of the controllable high-precision combustible shell of this embodiment is fixed on a metal copper sample plate using conductive glue. The sample needs to be gold-sprayed before testing, and the gold spraying time is 50 seconds. The fracture cross section of the sample is scanned with a high-magnification SEM, and the obtained SEM photo of the fracture cross section is as follows: Figure 2 As shown, from Figure 2 It can be seen that the RDX solid filler is dispersed more evenly, has good density, and the resin is in a good cured and cross-linked state.

[0030] The mechanical properties of the controllable high-precision combustible shell prepared in this embodiment were tested using a universal testing machine. At room temperature, samples were prepared according to national standard dimensions and subjected to tensile, bending and compression performance tests. The tensile performance curve is shown in Figure 2. Figure 3 As shown, from Figure 3 It can be seen that the average tensile strength is 6.462MPa; the bending performance curve is as follows Figure 4 As shown, from Figure 4 It can be seen that the average bending strength is 10.217MPa; the compressive strength performance curve is as follows Figure 5 As shown, from Figure 5 It can be seen that the average compressive strength is 36.091MPa. Figures 3 to 5 It can be seen that the controllable high-precision combustible shell has good mechanical properties.

[0031] Comparative Example 1: This comparative example differs from Example 1 in that the amount of methyl orange added in step 1 is 0, and the other steps and parameters are the same as in Example 1 to obtain the upper cover of the combustible cartridge case.

[0032] The upper cover of the combustible shell prepared in this comparative example without adding the photoinhibitor methyl orange is shown in the following photo. Figure 6 As shown, from Figure 6 It can be seen that the shape of the upper cover is irregular, the surface is rough, and the shape and size of the combustible charge shell upper cover cannot be precisely controlled.

[0033] Comparative Example 2: This comparative example differs from Example 1 in that the amount of methyl orange added in step 1 is 0.05 g, and the other steps and parameters are the same as those in Example 1 to obtain the upper cover of the combustible cartridge case.

[0034] The combustible cartridge cover prepared in this comparative example with a small amount of methyl orange added as the light inhibitor was rough in surface appearance, with obvious layering and unevenness, and with severe loss of details, making it impossible to accurately present subtle details in the design.

[0035] Comparative Example 3: This comparative example differs from Example 1 in that the amount of methyl orange added in step 1 is 0.3 g, and the other steps and parameters are the same as in Example 1 to obtain a combustible cartridge.

[0036] In this comparative example, the amount of methyl orange added as the photoinhibitor is relatively large, and the absorption of ultraviolet light energy is too strong. The remaining ultraviolet light energy cannot meet the initiation requirements of the photoinitiator, making 3D printing impossible.

[0037] A comparison of Example 1 with Comparative Examples 1 to 3 shows that only when the appropriate amount of the photoinhibitor methyl orange is added can high-precision 3D-printed combustible shell products be obtained. Without a photoinhibitor or with a small amount, the dimensional accuracy of the 3D-printed combustible shell products is poor. This is because, in a slurry system containing energetic fillers, the energetic fillers severely scatter UV light. This scattered energy triggers the curing of the surrounding resin, causing the cured edge to extend. Adding an appropriate amount of the photoinhibitor methyl orange absorbs the scattered energy, suppressing scattered light in non-target cured areas and leaving the edges of the target cured area clear, thereby achieving a 3D-printed combustible shell with controllable precision.

[0038] Example 2: The method of controllable high-precision light-curing 3D printing of a combustible shell in this embodiment is carried out according to the following steps:

[0039] 1. Weigh 100 g of polyurethane acrylic resin, 3 g of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (819), 70 g of isobornyl methacrylate (IBOMA), 60 g of 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX) crystal particles with an average particle size of 35 μm, and 0.2 g of silicon dioxide, and add them into a container in sequence. Stir in a dark environment at a rotation speed of 456 r / s for 2 h to obtain a slurry.

[0040] 2. Pour the slurry into the material tank of the light-curing 3D printer. The wavelength of the light source is 405nm, the power is 120mV, the printed layer thickness is 0.05mm, and the single layer exposure time is 2s. After 3D printing, a high-precision combustible shell is obtained; it includes an upper cover and a lower body.

[0041] The photo of the controllable high-precision combustible shell obtained in this embodiment is shown in FIG. Figure 7As shown in the figure, a is the lower body of the combustible charge case, and b is the combustible charge case with the upper cover. The dimensions of the upper cover and lower body of the controllable, high-precision combustible charge case obtained in this embodiment are consistent with those in the design drawings. The outer diameter error of the lower body is extremely small, at 25 microns. The surface is smooth and delicate, with no obvious layer marks, and can accurately reproduce the tiny details of the design. The layer thickness is uniform and thin, and the material utilization rate is high, so that post-processing is minimal or even unnecessary, saving time and cost.

[0042] The controllable, high-precision combustible cartridge case of this embodiment was subjected to mechanical property testing. At room temperature, tensile, flexural, and compressive performance tests were conducted using samples prepared according to national standard dimensions. The results showed an average tensile strength of 6.335 MPa, an average flexural strength of 10.085 MPa, and an average compressive strength of 36.147 MPa. These test data demonstrate that the controllable, high-precision combustible cartridge case exhibits excellent mechanical properties.

Claims

1. A method for controllable high-precision light-curing 3D printing of combustible shells, characterized in that: The method proceeds as follows:

1. Mix 100 parts of photocurable resin, 5 parts of photoinitiator, 25-80 parts of reactive diluent monomer, 50-90 parts of energetic filler and 0.1-0.2 parts of photoinhibitor in parts by weight to obtain a slurry; The light-curable resin is one or a combination of polyurethane acrylate, epoxy acrylate, polyester acrylate, and unsaturated polyester; The energetic filler is one or a combination of 2,4,6-trinitrotoluene, hexanitrohexaazaisopentazolidine, 1,3,5-trinitro-1,3,5-triazacyclohexane, and 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane; The photoinhibitor is one or a combination of carbon black, titanium dioxide, silicon dioxide, zinc oxide, zinc barium, methyl orange, Sudan III, methylene blue, and rhodamine B; 2. Add the slurry into the material tank of the light-curing 3D printer and perform 3D printing with a layer thickness of 0.025mm to 1.0mm. Use a UV light source with a wavelength of 254 to 435nm and a power of 100 to 120mV for light curing. The exposure time of a single layer is 2 to 3s. After 3D printing, a controllable, high-precision combustible shell is obtained.

2. The method for controllable high-precision light-curing 3D printing of combustible shells according to claim 1, characterized in that: The particle size of the energetic filler described in step 1 is in the range of 30 to 500 μm.

3. A method for controllable high-precision light-curing 3D printing of combustible cartridge cases according to claim 1 or 2, characterized in that: The photoinitiator described in step 1 is one or a combination of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 2,4,6-trimethylbenzoylphosphonic acid ethyl ester, phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide, and 1-hydroxycyclohexyl phenyl ketone.

4. A method for controllable high-precision light-curing 3D printing of combustible cartridge cases according to claim 1 or 2, characterized in that: The active diluent monomer in step 1 is one or a combination of monofunctional isobornyl methacrylate, ethoxyethoxyethyl acrylate, and tripropylene glycol diacrylate.

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